Brydon, J.

Rennie, D.A.

English

eCommons@USASK

Estimating the effect of management on landscape yields

University of Saskatchewan Research Archive

ESTIMATING THE EFFECT OF MANAGEMENT ON LANDSCAPE YIELDS J. Brydon and D.A. Rennie Saskatchewan Institute of Pedology University of Saskatchewan Saskatoon, Sask. For the last half century, summerfallow has been required and extensively used for adequate soil moisture accumulation and weed control in the Brown and Dark Brown soil zones of Saskatchewan. In recent years, soil conser-vation practices such as minimum tillage and chemical summerfallow have been emphasized (Lindwall and Dubetz 1983). Alternatives to conventional summer-fallow such as extended rotations and stubble management for snow water capture have been suggested and are under evaluation in various parts of the province (Campbell et al. 1983). Little is known about the performance of these systems on individual soil associations or on different slope positions within the landscape. A major goal of the Innovative Acres Program, ini ti-ated in 1981, was to evaluate the performance of cropping systems on various soil mapping units. This information would help to form recommendations regarding different management systems for individual mapped soils and help to attain maximum productivity and minimum soil degradation on these soils. The objectives of the study reported in this manuscript were to interpret the production and water data obtained for the Weyburn Association and to translate these yields to whole landscapes, or map units of the Weyburn Association. METHODS Using yield and moisture data from two farms located on Weyburn soils of the Dark Brown soil zone (Stoney Beach and Semans, Saskatchewan), linear regression equations were derived for yield as a function of total available 78 soil moisture (TAW) (growing season precipitation plus available soil moisture at seeding) for upper, mid and lower slope positions for four "simulated" management systems. These systems included standing stubble (ST), fall cultivated stubble (FC), chemical summerfallow (CMF), and conventional summerfallow (SMF). It was assumed that a relatively high and uniform fertility level had been maintained at both locations and no differences in WUE were to be expected at different slope positions due to fertility. This assumption unfortunately was incorrect, as production levels at the Stoney Beach location were low due to nitrogen limitations. One linear regression equation was formed by grouping all slope positions together. The calculated WUE for this equation was 75.5 kg ha- 1 cm- 1 • Moisture conservation efficiencies (CE), or the percentage of precipi-tation conserved as soil moisture, were estimated for the upper, mid and lower slope positions under these different management systems. The estimated CE's for each portion of the non-cropped period are shown in Table 1. Stored available moisture at seeding (AMS) was calculated as: CE. * PREC. J J AMS [ 1 J where: CE. = conservation efficiency of period j and PREC. J J pr eci pi tat ion (em) of period j. Precipitation data for the Saskatoon area was gathered from records compiled by the Saskatchewan Research Council. Growing season precipitation (GSP) was calculated as that falling between May 15 and August 15; all other dates were combined to provide fall, winter and spring precipitation for the years 1970 to 1985 inclusive (Table 2). The amount of total plant available soil moisture (TAW) was calculated as: TAW AMS + GSP [ 2] 79 Table 1. Estimated conservation effi ci enci es 1 (%) for upper, mid and lower slope positions for different management systems. Slope position Management Upper Mid Lower 1st winter Standing stubble 30 35 50 Fall cultivated stubble 20 30 45 Summer Conventional summerfallow 5 1 0 10 Chemical summerfallow 1 0 1 0 1 0 2nd winter Conventional summerfallow 1 5 1 5 25 Chemical summerfallow 20 20 30 1 Percentage of precipitation stored as moisture in the soil Table 2. Growing season and fall, winter and spring precipitation, 1970-1985, Saskatoon. Year 1970 1 971 1972 1973 1974 1975 1976 1 977 197 8 1979 1980 1 981 1982 1983 1984 1985 Ave. Growing season precipitation (em) 21 • 41 24.84 1 4. 66 1 4. 73 24.92 20. 17 1 8.1 8 1 4. 04 1 4. 58 1 4. 34 12.26 1 2. 71 24.94 21.1 1 0.05 1 9. 45 17.65 Fall, winter and spring precipitation (em) 1 27. 11 1 6. 94 19.88 1 6. 1 5 28.01 1 7. 56 18.03 1 6. 9 17.16 27.73 1 5. 42 18.33 13.82 26.74 1 6. 09 30.96 20.43 1 Fall, winter and spring precipitation is that which precedes the growing season, e.g. the value cited for 1970 is that which fell between the 1969 and 1970 growing seasons (15 Aug-15 May) 80 where AMS = estimated stored available moisture at seeding (em) and GSP Saskatoon growing season precipitation (em). From descriptions of the various Weyburn map units found in Saskatchewan (Saskatchewan Institute of Pedology, 1985) and discussion with soil sur-veyors, the relative distributions of upper, mid and lower landscape units and uncultivated areas for individual map units (W1- W14) were estimated (Table 3). Weyburn 6 (W6) map units were not included in this study due to significant calcareous and saline meadow profiles. The slope position yields were then translated into yields per map unit area for each map unit. Table 3. Distribution of landscape units for Weyburn map units (%) • Landscape unit Map unit Uncultivated Upper Mid Lower Distribution W1, W3 1 0 60 30 W2, W13, W14 30 40 1 5 1 5 W4, W8, W10 30 50 20 W5 20 50 1 5 1 5 W7 20 40 1 0 30 W9 40 35 1 0 1 5 W11 20 50 20 1 0 W12 20 60 20 All yields and production values for each map unit were calculated on a per unit area basis. That is, the uncultivated portions of some map units were fully considered when moisture and yield calculations were made for those map units. 81 Weyburn map unit yields for CMF and SMF were calculated for 1971 to 1985, while those of ST and FC were calculated for 1970 to 1985 inclusively. The different management systems could then be combined to simulate different cropping rotations and the relative performance of each cropping system on the different map units were evaluated. A number of assumptions or conditions were associated with each manage-ment system; they are described in the following: 1) CMF - fallow period of 21 months - weeds are controlled through the use of herbicides only - good weed control is maintained throughout the period - minimum or zero tillage system 2) SMF - fallow period of 21 months - 4 or 5 tillage operations throughout fallow period required (Anderson, 1 971 ) 3) ST stubble left standing in fall - fall application of herbicides provides good weed control 4) FC - stubble is incorporated in the fall; little residue left on surface RESULTS Table 4 shows simple statistics for the estimated AMS of each slope position for the 1970 to 1985 period for the four management systems. Stubble management was shown to conserve a mean 2 em more moisture on the U slopes, and 1 em more on theM and L slopes than did cultivated stubble management. CMF conserved a mean of 2 em more on the U slope positions, and 1 em more on the M and L slopes than did SMF. Table 4 shows that AMS increased from upper to lower slope positions, and mean AMS increased in the order FC < ST < SMF < CMF. Grevers et al. (1985) reported results from 12 site years in Saskatchewan, where zero tillage was compared with conventional tillage and found similar trends; soil water recharge increased in the order conventional till fall cultivated < conventional till stubble (tilled one 82 Table 4. Simple statistics for predicted available moisture at seeding for each slope position for four management systems, 1 970-85. Slope Mean Standard deviation c. v. Management position (em) (em) (%) Conventional u 9.8 1.4 1 3. 8 surnmerfallow M 11.7 1.7 1 4. 5 (1971-85) L 1 6. 6 2.3 13.8 Chemical u 11.7 1.5 1 2. 8 s urnm er fall ow M 12.7 1.7 1 3. 3 (1971-85) L 17.6 2.3 13.1 Standing u 6. 1 1.7 27.3 stubble M 7.2 2.0 27.3 ( 1970-85) L 1 o. 2 2.8 27.3 Fall culti- u 4. 1 1.1 27.3 vated stubble M 6.1 1.7 27.3 ( 1970-85) L 9.2 2.5 27.3 week prior to seeding) and conventional till < zero till. Simple statistics for predicted yields on SMF, CMF, STand FC management systems for the three slope positions during the period 1970 to 1985 are given in Table 5. Mean ST:SMF ratios for the U, M and L slope positions were 0.80, 0.78 and 0.74, respectively. The ST:SMF ratios for the three landscape units increased significantly, and became similar when a wet winter followed a dry winter. This occurred four times in the 16 year study period (1973-74, 1978-79, 1982-83 and 1984-85). The range of the average ST:SMF ratios were very similar to those reported by other workers (Austenson et al. 1970; Kirkland and Keys 1981; Campbell et al. 1983). The CV's in Table 5 show that yield variability decreased from the upper to lower slope positions on each management system. Estimated yield variability was lower for both fallow systems (CMF and SMF) than for the 83 Table 5. Simple statistics f'or predicted yield f'or each slope position for four management s ys terns, 1 970-"85. Slope Mean Standard deviation c. v. Management position (kg/ha) (kg/ha) (%) Conventional u 1297 392 30.2 surnmerf allow M 1 438 398 27.7 (1971-85) L 1 81 2 420 23.2 Chemical u 1 439 401 27.8 s urnmerf allow M 1 51 3 403 26.6 (1971-85) L 1 887 425 22.5 Standing u 1 040 443 40.7 stubble ~1 111 7 435 38.9 (1970-85) L 1348 475 35.3 Fall cul ti- u 886 401 45.3 vated stubble M 1 040 423 40.7 (1970-85) L 1 271 461 36.3 recrop ST and FC systems. Standing stubble yields were approximately 17% higher than those under fall cultivated stubble on the upper slope positions. The slope position yield data were used to calculate yields for the different Weyburn map units for the four management systems for the same 16 year study period, based on the percentages of upper, mid, lower and uncultivated areas within each map unit. Mean available moisture at seeding for each Weyburn map unit under the four management systems is shown in Table 6. Generally SMF was found to have 8 to 11% less moisture at seeding than did CMF. Soil moisture reserves on ST were approximately 62% of SMF, and 56% of those for CMF. Map units which had been fall cultivated had approi xmately half the available moisture of those that had been chemically fallowed, and 81 to 86% of those under stubble. Available moisture at seeding was highest for W1 and W3, and lowest for W9. This order essentially reflects the different percentages of lower slope 84 Table 6. Simple statistics for predicted available moisture at seeding of Weyburn map units under four management systems, 1 970-1 985 .r Map unit W1, W2, W4, W3 W13,W14 W8,W10 W5 W7 W9 W11 W12 Standing Stubble (1970-85) Mean (em) 8.0 7.3 7.5 7.4 7.3 7.0 7.6 7.6 Std. Dev. (em) 2.2 1.7 2.0 1.7 1.4 1.6 1.9 2.1 c.v. (%) 27.3 27.3 27.3 27.3 27.3 27.3 27.3 27.3 Chemical Summerfallow (1971-85) Mean (em) 1 4. 0 13.2 1 3. 4 1 3. 3 13.1 1 2. 8 1 3. 6 1 3. 5 Std. Dev. (em) 1.9 1.5 1.8 1.5 1.2 1.4 1.6 1.8 c.v. (%) 13.2 13.1 13. 1 13. 1 1 3. 1 13.0 13. 1 1 3. 1 Conventional Summerfallow (1971-85) Mean (em) 13.0 11.9 1 2. 1 1 2. 1 11.9 11.4 12. 3 1 2. 3 Std. Dev. (em) 1.8 1.4 1.7 1.5 1.2 1.4 1.6 1.7 c.v. (%) 1 4. 1 1 4. 1 1 4. 1 1 4. 2 1 4. 1 1 4. 1 1 4. 1 1 4. 1 Fall Cultivated Stubble (1970-85) Mean (em) 6.8 6.0 6. 1 6.2 6.0 5.5 6.3 6.3 Std. Dev. (em) 1.9 1.4 1.7 1.4 1.1 1.3 1.6 1.7 c.v. (%) 27.3 27.3 27.3 27.3 27.3 27.3 27.3 27.3 positions within each map unit. Those map units with a small proportion of lower slope positions will provide the lowest mean available moisture at seeding. The range in AMS was approximately 1 em for each management system. Means, standard deviations, and CV's for all estimated Weyburn map unit yields per unit area are shown in Table 7. CMF and SMF map unit yields showed less variability than did ST or FC map unit yields. This has often been reported in the literature (Anderson 1971; Austenson et al. 1970; Austenson and Khatri 1972; Campbell et al. 1983), and is a major reason why farmers continue to practice summerfallow. To assess the relative performance of different cropping rotations on 85 Table 7. Simple statistics for predicted Weyburn map unit yields per map unit area under four management systems, 1970-1985. Map unit W1, W2, W4, W3 W13,W14 W8, W 1 0 W5 W7 W9 W11 W12 Standing Stubble (1970-85) Mean ( kg/ha) 1178 961 11 40 969 789 942 1 036 1148 Std. Dev. 445 372 439 373 306 369 397 440 ( kg/ha) c. v. (%) 37.8 38.7 38.5 38.5 38.7 3 9. 1 38.3 38.3 Chemical Summerfallow (1971-85) Mean (kg/ha) 1 61 8 1320 1566 1 328 1082 1294 1 422 1573 Std. Dev. 409 345 406 345 284 344 366 406 (kg/ha) c. v. (%) 25.3 2 6. 1 25.9 26.0 26.2 26.6 25.7 25.8 Conventional Summerfallow (1971-85) Mean ( kg/ha) 1536 1236 1 4 71 1250 1 01 6 1203 1 3 41 1485 Std. Dev. 404 339 400 340 279 337 3 61 401 ( kg/ha) c. v. (%) 26.3 27.4 27.2 27.2 27.5 28.0 26.9 27.0 Fall Cultivated Stubble (1970-85) Mean (kg/ha) 1094 872 1 040 889 720 845 951 1055 Std. Dev. 431 358 423 360 295 354 383 425 ( kg/ha) c. v. (%) 39.4 41.0 40. 1 40.6 40.9 41.8 40.3 40.3 each Weyburn map unit, five different rotations were simulated for this study. Three rotations (A, Band C) included CMF; two were set up as flex-ible cropping systems (based on a critical minimum level of available moisture at seeding of 6.5 em), and one as an extended five year rotation (chemical fallow-W-W-W-W). Two regular rotations (D and E) included a F-W and a F-W-W rotation, respectively. The flexible rotation A had no limit on the number of CMF periods allowed. The second IF rotation (B) allowed a CMF period only once in three years; each 3-year period had to contain one ST 86 yield. This procedure was followed for each map unit. The total production per unit area (tonnes/ha) for each map unit under the five simulated rotations for the 16-year period is shown in Figure 1. As the number of cropped years increased, total production increased. The flexible rotation B was most successful in terms of total production on map units W1 , W3 and W1 2, and was practically equal to that of rotation C for map units \-14, W8 and W10. Adequate AMS (>6.5 em) was often present during the 16 years, and infrequent CMF periods Here required. The 5-year fixed rotation (C) was most favorable for map units W2, W13, W14, W5, W9 and H11 in terms of total production. 20 16 EJ Rotct1on . 16 - 111 (1:1 14 Rotation -E (l't @.11 c 12 c 0 II -c tO Rotation 0 --u s ~ "10 e • Rotet1on Q.. 6 c ..... 0 4 1-2 Rotet1on Weybum Mep Unit Figure 1. Total Heyburn map unit production per unit area for rotations during 1970-85 (tonnes/ha). 87 A 6 c I) E All average recrop yields on W7 were below the acceptable minimum yield, that is, less than 70% of average SMF yield, because of the high percentage of uncultivated land (30%) within this map unit. This indicated that a F-W rotation is the only feasible rotation for this map unit. CONCLUSIONS Even though the yields resulting from the simulated rotations were substantially lower than "real yield values", they showed distinct trends, and for some of the map units, indicated which rotations are most suitable for given map units. The approach used in this study allowed for an evaluation of different cropping systems on different simulated map units, and thus related yields and productivity to both management and landscape. This approach could easily be used for mapping units of soil associations other than Weyburn to provide further information about the relative performance of different rotations on different landscapes. Recommendations for improved management systems for individual map units could be more easily determined. Anderson, C.H. 1971. semi ar i d region . REFERENCES Comparison of tillage and chemical summerfallow in a Can. J. Soil Sci. 51: 397-403. Austenson, H.M. and Khatri, S.R. 1972. Relative yields of wheat, barley and oat cultivars on summerfallow and stubble land. Can. J. Plant Sci. 52: 659-666. Austenson, H.M., Wenhardt, A. and White, W.J. 1970. Effect of summer-fallowing and rotation on yield of wheat, barley and flax. Can. J. Plant Sci. 50: 659-666. Campbell, C.A., Read, D.W.L., Zentner, R.P., Leyshon, A.J. and Ferguson, W.S. 1983. First 12 years of a long-term crop rotation study in southwestern Saskatchewan - yields and quality of grain. Can. J. Plant Sci. 63: 91-108. 88 Grevers, M.C., Kirkland, J.A., de Jong, E. and Rennie, D.A. 1985. Soil water conservation under zero and conventional tillage farming systems on the prairies. International Soil Tillage Research Organization, 1Oth Conference, July 8-12, 1985. Univ. of Guelph, Guelph, Ontario. 18 p. Kirkland, K.J. and Keys, C.H. 1981. The effect of snow trapping and cropping sequence on moisture conservation and utilization in west-central Saskatchewan. Can. J. Plant Sci. 61: 241-246. Lindwall, C .w. and Dubetz, S. 1983. Conservation tillage. Proc. Second Annual Western Provincial Conference on Rationalization of Water and Soil Research and Management: Soil Erosion and Degradation. Saskatoon, Sask., Nov. 29-Dec. 1, 1983. pp. 121-129. 89 

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Estimating the effect of management on landscape yields

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